MC33035 Motorola, MC33035 Datasheet - Page 23

• Manufacturer Part Number: MC33035
• Description: BRUSHLESS DC MOTOR CONTROLLER
• Manufacturer: Motorola

Brush Motor Control
DC motors, it may also be used to control DC brush type
motors. Figure 46 shows an application of the MC33035
driving a MOSFET H–bridge affording minimal parts count to
operate a brush–type motor. Key to the operation is the input
sensor code [100] which produces a top–left (Q
bottom–right (Q
pin is at logic [1]; top–right (Q
realized when the Forward/Reverse pin is at logic [0]. This
code supports the requirements necessary for H–bridge
drive accomplishing both direction and speed control.
width modulated frequency of approximately 25 kHz. Motor
speed is controlled by adjusting the voltage presented to the
noninverting input of the error amplifier establishing the
PWM’s slice or reference level. Cycle–by–cycle current
limiting of the motor current is accomplished by sensing the
voltage (100 mV) across the R
H–bridge motor current. The over current sense circuit makes
it possible to reverse the direction of the motor, using the
MOTOROLA ANALOG IC DEVICE DATA
Though the MC33035 was designed to control brushless
The controller functions in a normal manner with a pulse
10 k
10 k
0.005
Fwd/Rev
+12 V
Enable
Faster
3
) drive when the controller’s forward/reverse
10
22
17
18
11
13
12
4
5
6
3
7
8
Error Amp
Reference
Regulator
25 A
Oscillator
4
S
), bottom–left (Q
PWM
resistor to ground of the
Undervoltage
Lockout
Figure 46. H–Bridge Brush–Type Controller
Shutdown
Thermal
Gnd
R
S
S
R
Decoder
Position
Rotor
2
) drive is
1
Q
Q
) and a
16
MC33035
normal forward/reverse switch, on the fly and not have to
completely stop before reversing.
LAYOUT CONSIDERATIONS
motor control circuits on wire–wrap or plug–in prototype
boards. High frequency printed circuit layout techniques are
imperative to prevent pulse jitter. This is usually caused by
excessive noise pick–up imposed on the current sense or
error amp inputs. The printed circuit layout should contain a
ground plane with low current signal and high drive and
output buffer grounds returning on separate paths back to the
power supply input filter capacitor V
capacitors (0.1 F) connected
amp noninverting input may be required depending upon
circuit layout. This provides a low impedance path for filtering
any high frequency noise. All high current loops should be
kept as short as possible using heavy copper runs to
minimize radiated EMI.
close to the integrated circuit at V
Do not attempt to construct any of the brushless
Brake
23
I
Limit
24
14
2
1
21
20
9
15
19
20 k
DC Brush
Motor
22
Fault
Ind.
0.001
CC
1.0 k
1.0 k
, V
M
C
. Ceramic bypass
, V
ref
Q
Q
1
2
*
*
22
and the error
M
1.0 k
+12 V
23
R
Q
Q
S
4
3
*
*